Endothelial nitric oxide synthase (eNOS) signaling in the vascular wall is a key determinant of vascular homeostasis and is regulated by diverse signaling pathways. This project explores the regulation of eNOS activity by S-nitrosylation, the redox-mediated adduction of nitric oxide-derived nitrosyl groups to the cysteine thiols of proteins. The hypothesis of this proposal is that S-nitrosylation is a controlled post-translational modification that is an important regulator of eNOS activity in vascular endothelial cells. In support of this hypothesis, we show data that eNOS activity in endothelial cells is regulated by dynamic, receptor-modulated enzyme S-nitrosylation. Experiments are proposed to identify the endothelial cell signaling pathways that mediate changes in eNOS S-nitrosylation and to explore the biochemistry of eNOS S-nitrosylation using purified protein. Ultimately, these studies may identify potential targets for pharmacological intervention in the treatment of cardiovascular diseases. [unreadable] [unreadable]